The long-term objective is to identify the specific cellular mechanisms involved in the damage, protection and recovery from UVA (290-320 nm) and UVB (320-400 nm) irradiation. Increased exposure to solar UVA/UVB irradiation is related to the rise in skin cancer. Human health is affected by increased UVA/UVB due to (1) the erosion of the stratospheric ozone layer; (2) more time spent outdoors in recreational activities, and (3) increased use of tanning beds. On an average day in the United States, more than one million people visit a tanning salon and expose themselves to UVA radiation with intensity up to 10 times higher than sunlight depending on the type of tanning bed used. During the last 3 years, use of tanning beds increased from 7% among 14-year-old girls to 16% by age 15, and 35% by age 17. Studies show a connection between the increased use of tanning beds and a higher incidence of skin cancer. Approximately 7,500 deaths will be attributed to melanoma in 2003. The combination of high intensity UVA tanning bed irradiation and solar UV irradiation significantly increases tumor incidence and impairs the ability of cells to repair DNA damage. Highly reactive oxygen radicals mediate the damaging effects of UVA irradiation. Proteins are one of the major targets of reactive oxygen radicals. Using human keratinocytes and fibroblasts, a specific aim of this study will be to quantify the extent of protein oxidation after standard doses of irradiation delivered under tanning bed vs. solar irradiation intensity (fluence levels). Changes in activity levels of key antioxidant enzymes will be correlated with protein oxidation. Selenium, known to induce genes in oxidative defense, will be used to determine its potential for reducing UVA-induced oxidative modification of proteins. The research methods will include protein gel electrophoresis and western blots to identify and quantify oxidized proteins under a variety of irradiation conditions to determine if changes in intensity, dose or exposure cycles can decrease protein oxidation. This research is significant because it will help to develop strategies to minimize the harmful effects of increased use of tanning beds despite the published warnings of their health hazards; it will contribute to the development of photo-protective and photo-therapeutic strategies in medicine. This research will have an impact on the undergraduate teaching environment by providing multiple research opportunities for students, who are preparing for careers in the health-related professions, to develop critical thinking skills by designing and conducting experiments, collecting data and interpreting their significance to human health.